Of the various complexities floating around the EU referendum, one seems to inspire more head-scratching than most. The question of whether Britain should have two referendums rather than one has been around for a while – even George Osborne was forced to reject it on Newsnight last week. Dominic Cummings, Vote Leave’s campaign director, was advocating a second referendum in a Bloomberg interview only yesterday, while Leave.EU’s Arron Banks dismissed it as a “cheap trick” on Monday. But where does the idea come from, why is it being suggested and would it be a good idea?

The genesis of a second referendum lies in the fundamental question which inhabits every polling booth: security or risk? That’s a key dividing line in any election, and arguably even more so in a referendum. Do you stick with Gordon Brown, who’s held high office for years, or do you think it’s time for a change and back Cameron? Do you want to keep First Past The Post, which has served us for so long, or do you want AV, to shake up a malfunctioning political system? Should Scots stay in the good old Union, or cut themselves free of broken Westminster politics?

Both Leave and Remain campaigns are already racing to paint their opponents as offering the true risky option in the EU referendum. Pro-EU campaigners seek to conjure up fears that Brexit would be a leap in the dark, while their anti-EU opponents argue that staying in thrall to Brussels puts us on a road to less democracy and a withering economy.

The conventional wisdom is that those pressing for change are most vulnerable to the electorate’s fear of risk. ‘Better the devil you know’ is believe to be a compelling mantra for previously undecided voters. Certainly the AV and Scottish independence ballots would seem to bear that out – though of course the same electorate regularly opt for change when it comes to elections, and the pro-change side do win sometimes, so evidently it isn’t a strict rule.

The second referendum concept is born of that strategic challenge. If your opponents intend to raise endless fears about change being too risky, then giving people another vote further down the line could function to blunt their argument. And when it does come to a second vote, by that time people might already in the mindset of considering the proposed change to be a real, plausible future.

Downing Street reportedly feared that Salmond would pursue such an approach on Scottish independence for all these reasons – so it isn’t that surprising that it has come to mind among some of those thinking about the EU referendum. In a speech hosted by ConservativeHome in 2012, David Davis proposed a double referendum on the EU, which we reported as follows:

‘First, a “Mandate referendum” would take place, to give a Conservative Prime Minister a mandate “to get as close as possible to the trading alliance, the common market we all voted for in 1975”. If passed, voters would have made it clear that they want to leave the EU as it presently stands. Next, if the people had voted “Yes”, there would be a renegotiation with the aim of getting as close as possible to that trading alliance. And finally, there would be a second referendum – a “Decision Referendum” – which would give voters the option of accepting the renegotiation terms. Mr Davis wants the Mandate Referendum as well as the Act to take place in this Parliament.’

Of course, that didn’t happen – the Prime Minister decided to hold a renegotiation first, followed by a referendum to either stay in on the renegotiated terms (whatever they may prove to be) or to leave.

Cummings’ version of the concept, which he mulled in a blogpost last June, is that the forthcoming referendum would be on whether to Remain in the EU on Cameron’s renegotiated terms or to Leave. After that referendum, the Government would enter negotiations to Leave the EU – as laid out in Article 50 of the Lisbon Treaty – and a second referendum could take place on the outcome of those negotiations. Brussels could, perhaps, offer better terms during those negotiations, rendering the process one from which Britain would gain either way.

The idea has its pros and cons. On the plus side:

The blunting of the risk argument – on the basis that it wouldn’t be a completely final decision – would likely provide some reassurance about voting Leave. If you want to leave the EU, then this could be a route to reassure undecided voters, win the first referendum and then win the second by virtue of people becoming accustomed to the idea. As Cummings put it to Bloomberg, the plan seeks to make the initial referendum ‘a free hit’.

If you do want to stay in a sizeably reformed EU, then an initial referendum to put the frighteners on Brussels could deliver better terms than Cameron’s renegotiation. According to the Sunday Times, Boris has reportedly told ‘friends’ that an initial vote to Leave would constitute playing hardball, generating a more productive renegotiation before the second referendum.

And on the down side:

EU law may stand in the way. Over at the UCL Constitution Unit, Alan Renwick recites the specific requirement of Article 50 – which makes no provision for the idea of a Member State starting negotiations to leave but then deciding to stay on improved terms. ‘It [the second referendum] would require a negotiation for revised membership terms, when what Article 50 provides for is a negotiation to cease membership,’ he writes. That’s arguably deliberate – the EU designing the rules of its own club precisely in order to make leaving look like a daunting task, and providing limited scope for using a threat to leave as a stick with which to demand a renegotiated relationship (indeed, such behaviour is a good argument for why this is not a desirable club to be in). This element shouldn’t be overstated, though: details of the Treaty matter, but only to a degree; ultimately, Parliament and the Government can do what they like and vote to leave treaties however they might wish.

While a dual referendum approach might reassure wavering voters, it might simultaneously lose the enthusiasm of voters who definitely, absolutely want to leave the EU. After all, if the first referendum didn’t necessarily mean getting to leave the EU after all, how safe is it to assume that nailed-on Leave voters will come out and vote in it?

The whole proposal is more than a little confusing. A referendum is meant to present a straightforward choice on a topic – as a matter of fact, that is often the criticism levelled at the concept of referendums by their opponents. Given the large task of debating our relationship with the EU lies ahead, is it necessarily wise to add the challenge of explaining a further ballot, more negotiations and the dry material of articles of the Lisbon Treaty?

Finally, it must be said that the idea raises the hackles of some hardcore eurosceptics. Holding a second referendum is not a concept which has an honourable history in EU politics – in the past the Dutch, the Danes and the Irish have at one time or another rejected EU treaties by means of a referendum, only to be made to vote again, at which point the rejections were reversed. This instance might be different, a second referendum demanded by eurosceptics rather than by the Eurocrats, but the taint of that memory will be hard to shake off. For some elements in UKIP, in particular, who already claim that Vote Leave is an elaborate con trick to keep Britain in the EU, the appearance of such a tactic is fuel to their conspiracy theory fire.

The second referendum is an elegant strategic solution to a strategic challenge – the Chancellor’s eagerness to reject it out of hand suggests that he knows that it could pose a serious problem for the Remain campaign. But as well as its benefits it also has attendant risks.

More importantly, though, even if it were a perfect idea the question remains: how could it actually come about? The single referendum is already laid down in statute, and thus far the Government shows no inclination to change that. For Cummings, the moment when it might be feasible is when Cameron comes back with his renegotiation – and it would need a Cabinet heavyweight to stick their neck out and demand it, on the basis that the Prime Minister’s deal is insufficient. That’s a very big ask, and he only has a very narrow window in which to get an answer.